Olefin copolymer modified with a hydroxybenzoic acid



United States Patent 3,274,158 OLEFIN COPOLYMER MODIFIED WITH A HYDROXYBENZOIC ACID Stanley Tucker, Wilmington, Del, assignor to E. I. du

Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware No Drawing. Filed May 24, 1965, Ser. No. 458,372

3 Claims. (Cl. 26062) This application is a continuation-impart of my copending application Serial No. 148,049, filed October 27, 1961, and now abandoned, which in turn is a continuationin-part of my application Serial No. 800,665, filed March 20, 1959, and now abandoned.

This invention relates to the manufacture of thermoplastic polymeric films. More particularly, it relates to the preparation of polyhydroc-arbon films suitable for conversion to bags, containers and similar packages.

The invention will be described primarily as it applies to polyethylene films. However, it will be clear that the invention is equally applicable to shaped structures of all types composed of polymers of alpha-olefins in general. Thus, filaments, foils, rods, tubes, as well as selfsupporting films, are embraced by the present invention.

The statements regarding prior polyethylene products and V the utility of the present invention are equally applicable to polymers of propylene, butylene, styrene, pentene-l, hexene-l, heptene-1, octene-l, decene-l, 3-methyl butene- 1, 4-methyl pentene-l, 4,4-dimlethyl pentene-l and isobutylene, etc., as well as polymers of ethylene.

Polyethylene, in the form of a self-supporting film, displays many properties which make it particularly desirable as a packaging film. The polyethylene film is characterized by high impact strength, high tenacity, high elongation combined with chemical inertness and low permeability to water vapor. However, polyethylene films lack some requisites for some important applications. The most outstanding is its lack of adherability. Thus, printing, a necessary treatment for successful use of packaging materials, is performed With great difficulty due to the lack of adherability of printing inks to the films surface. Coatings and laminates, useful for special purposes such as improving heat-sealability, etc., are diflicult to apply because of the films lack of adherability to itself and other materials. Another property lacking in these polymers in the form of films is stiffness. The limpness apparent in many polyhydrocarbon films, particularly polyethylene film, militates against their use in conventional bag-making and bag-processing machines. Still another property that can be improved is the polymers stability to light.

One object of the present invention is a process for remedying the above-described situation, i.e., a process for improving the above properties without affecting adversely the desirable properties of the polymer. Another object is to form novel polymeric compositions that display improved properties, particularly improved adherability to itself and other materials, increased stifi'ness and/or increased stability to light. Other objects will appear hereinafter.

The objects are accomplished by a polymeric composition comprising a modified copolymer of 65-99 mole percent, preferably 90-97 mole percent, of an alpha-olefin, such as ethylene, which provides in said copolymer a recurring group having the structure:

H H l l wherein R is hydrogen or alkyl of 1-8 carbon atoms; and 1-35 mole percent, preferably 3-10 mole percent, of

propadiene, said copolymer having been modified by reaction With a hydroxyl-containing aromatic acid such as salicylic acid, meta-hydroxy-benzoic acid and para-hydroxybenzoic acid, which provides in said copolymer a resulting 1-35 mole percent of one or more groups, in a random selection of each, from the group consisting of:

where Z is the monovalent hydroxybenzoyl radical.

The process involves first copolymerizing 65-99 mole percent of the alpha-olefin with -1 mole percent of propa diene by subjecting the monomers, preferably in a liquid hydrocarbon or halogenated hydrocarbon such as hexane, benzene, toluene, tetrachloroethylene, bromobenzene, chlorobenzene, etc., to a temperature of to 300 C. and a pressure of 1-1000 atmospheres in the presence of a coordination catalyst; isolating the resulting polymer; and, thereafter, reacting the polymer with a hydroxyl-containing aromatic acid.

A coordination catalyst may be' defined in its broad- 7 est sense as one formed by the reaction of a reducible polyvalent metal compound with an amount of a reducing agent sufiicient to reduce the valence of the metal component. Specifically, the catalyst is composed of:

(A) A compound containing at least one metal of the group consisting of metals of Groups IVa, Va and VIa of the Periodic Table, iron, cobalt, copper, nickel and manganese, said metal having directly attached thereto at least one substituent lfrom the group consisting of halogen, oxygen, hydrocarbon and O-hy drocarbon; and

(B) A reducing compound selected from the group consisting of metal hydrides and compounds having a metal of Groups I, II and III of the Periodic Table, said metal being above hydrogen in the electromotive series of the metals, attached directly through a single bond to a carbon atom, said carbon atom selected from the group consisting of trigonal carbon and tetrahedral carbon.

In the above definitions, Periodic Table means Mendeletfs Periodic Table of the Elements, 25th ed., Handbook of Chemistry and Physics, published by the Chemical Rubber Publishing Co.

Ordinarily, catalytic amounts of the components of the catalyst system may be used in the first step of the process. Thus, component (A) may comprise 0.01-20 millimoles or higher, preferably 0.2-20 millimoles, per liter of solvent plus monomers. The mole ratio of component (B) to component (A) in the catalyst system should be at least 1:1, preferably 1:1 to 100:1.

Component (A) in the catalyst system has been defined as a compound containing at least one metal sedium tetrachloride, vanadyl trichloride, tantalum pentabromine, cerium trichloride, molybdenum pent achloride, tungsten hexachloride, cobaltic chloride, ferric bromide, tetra(2-ethylhexyl)-titanate, tetrapropyl titanate, titanium oleate, octylene glycol titanate, triethanolamine titanate, tetraethyl zirconate, tetra(chloroethyl)-zirconate, and the like.

Component (B) in the catalyst system has been defined as a reducing compound selected from the group consisting of metal hydrides and compounds having a metal of Groups I, II and III of the Periodic Table above hydrogen in the electromotive series, attached directly through a single bond to a trigonal or tetrahedral carbon atom. A trigonal carbon atom is a carbon atom having two single bonds and a double bond;

| Groups which may be attached to a metal, which metal is attached to a trigonal carbon atom, are aryl groups or aryl-alkyl groups. By tetrahedral carbon atom is meant a carbon atom having four single bonds;

l Groups which may be attached to a metal, which metal is' attached to a tetrahedral carbon atom, are alkyl groups, aryl groups, alkylaryl groups and alkenyl groups. Specific examples of useful reducing agents included in this definition are phenyl magnesium bromide, lithium aluminum tetraalkyl, aluminum trialkyl, dimethyl cadmium, diphenyl tin, and the like.

Useful combinations of component (A) and component (B) compounds for use as catalyst systems in the invention include the following:

Vanadyl dichloride (VOCl plus aluminum diisobutyl butoxide Vanadyl trichloride (VOCl plus aluminum triisobutyl Vanadyl trichloride (VOCl plus aluminum hydride Vanadyl trichloride (VOCl plus lithium butyl Vanadium dichloride (VCl plus aluminum triisobutyl Vanadium trichloride (VCl plus aluminum isobutyl dichloride Vanadium tetrachloride (VC1 plus aluminum isobutyl dibutoxide Vanadium tetrachloride (VC1 plus aluminum triisobutyl Vanadium tetrachloride (VCl plus aluminum hydride 2-ethyl hexyl vanadate plus aluminum triisobutyl Titanyl dichloride (TiOCl plus aluminum isobutyl dichloride Titanium tetrachloride (TiCl) plus ethyl magnesium bromide I Titanium tetrachloride (TiCl plus aluminum triisobutyl Titanium tetrachloride (TiCl plus lithium aluminum Polymerization is preferably carried out in a solvent medium. Among the solvents which have been found useful in this step are hydrocarbons and halogenated hydrocarbons: hexane, benzene, toluene, cyclohexane, bromobenzene, chlorob'enzene, o-dichlorobenzene, tetrachloroethylene, dichloromethane and 1,1,2,2-tetrachloroethane. Heterocyclic compounds such as tetrahydrofuran, thiophene and dioxane may also be used.

The reaction conditions, temperature and pressure, at which polymerization is performed may be extremely mild. Temperatures of the reaction may range from 40 to 300 C. and pressures of 1 atmosphere to 1000 atmospheres may be used successfully. The optimum conditions of temperature and pressure are 0300 C. and not more than 500 atmospheres respectively.

As an illustration of a method contemplated for carrying out the present invention, the catalyst system, e.g., vanadyl trichloride and aluminum triisobutyl, is mixed in the hydrocarbon solvent, e.g., n-hexane, under a blanket of nitrogen gas. Component (A), vanadyl trichloride, may be present to the extent of about 5 millimoles and component (B), aluminum triisobutyl, may be present to the extent of about 10 millimoles. After stirring for about ten minutes at a temperature of about 25 C., the nitrogen supply is cut off and the gas stream composed of ethylene and/or other hydrocarbon monomer or monomers having terminal ethylenic unsaturation with propadiene in the desired mole ratio is passed into the catalyst suspension. Alternatively, the monomers may be introduced first into the reaction vessel, followed by introduction of the catalyst. The order of adding catalyst and monomers is not critical to the present invention. After sufiicient polymer is built up, the gas flow is stopped and water, methanol, ethanol or a similar low molecular weight alcohol, is added to destroy the catalyst. The copolymer or terpolymer (depending on the number of monomers used), is then isolated and purified in a manner known to those skilled in the art.

The mole ratio of propadiene-to-ethylene and/or other hydrocarbon monomer reacted should be such that the product of this step is composed of 1-35 mole percent propadiene (preferably 3-10 mole percent) and 99-65 mole percent (preferably 9790 mole percent) of the other hydrocarbon monomer or monomers. It has been found that the reaction is very efficient so that a reaction mixture of about 1-35 mole percent propadiene and about 99-65 mole percent of the remaining monomer or monomers usually will provide the desired product.

The product of this step is a substantially linear polymer having pendant vinyl and methylene groups and having an inherent viscosity of at least 0.3. The d-ilferent pendant groups will result from the fact that propadiene will copolymerize with monomers by more than one mechanism. Thus, propadiene will appear in a carbon-to-carbon chain with a pendant methylene group:

or it will appear in the carbon-to-carbon chain with a pendant vinyl group:

or any combinations of these. Most copolymers will contain some of each of the above types of structure, i.e., copolymers with propadiene will usually have some pendant methylene groups and some pend-ant vinyl groups. The present invention also contemplates copolymers with propadiene in the form of block copolymers, random copolymers or combinations of block and random. The determination of pendant vinyl groups and pendant methylene groups can be accomplished by In-. frared Spectral Techniques known to those skilled in the art, including those described by W. M. D. Bryant and R. C. Voter in Journal of American Chemical Society 75, 6113 (1953), and F. W. Billmeyer in Textbook of Polymer Chemistry, chapter 7, Interscience Publishers (1957).

In the modifying step, the polymer composed of 1-35 mole percent propadiene is reacted with the hydroxylcontaining aromatic acid. The polymer can be in the form of a particulate mass or a fiber or a film. Reaction can be carried to any degree. Preferably, the polymer is shaped into a structure in ways well known to those skilled in the art prior to reaction. Thus, the polymer can be melt pressed at a temperature of about 150 C. or higher to form a film. The reaction can be effected with the entire polymeric structure or reaction can be limited to the surface of the structure.

The reaction of the hydroxyl-containing aromatic acid with the ethylene/propadiene copolymer can be carried out in a suitable solvent such as nitrobenzene, carbon disulfide, or the like, in the presence of a Friedel-Crafts catalyst such as aluminum chloride, boron trifluoride, or the like. The mixture is maintained for a sufiicient time to complete the reaction in a temperature range of about 50 to 150 C., after which the product is isolated, purilied by washing, dried, and, thereafter, pressed into a film for examination.

The time required for contacting the copolymer with the hydroxyl-containing aromatic acid depends on a number of factors such as temperature, composition of copolymer, and the specific result desired. Thus, in effecting treatments with the aromatic acid to increase adherability of film surfaces, the time required for reaction is determined by carrying out the reaction and testing film surface adherence to itself or to other materials which may be adhered to it after different time periods. Higher temperatures, higher concentrations of the hydroxyl-containing aromatic acid and higher percentages of propadiene in the copolymer tend to reduce the time necessary for reaction. After reaction is complete, the product is separated from the mixture, washed with water and dried.

The copolymers containing the hydroxybenzoyl groups are characterized by excellent light stability.

It has been found that since the chemical transformations occur on unsaturated groups appended to the polymer chain, while the chain itself is essentially unaffected, the desired characteristics of the parent polymer are retained in the final product. Thus, the final product displays satisfactory tensile strength, impact strength, flex resistance, etc., while the property improved such as its adherence to printing inks, coatings, other films such as regenerated cellulose and polyethylene terephthalate, is increased substantially. Furthermore, it has been found that the adherability achieved shows no tendency to disappear upon aging.

The following examples are intended to provide a clearer understanding of the present invention. They should not be considered to limit the scope of the invention.

Example 1 To 250 ml. of anhydrous cis-Decalin under a blanket of nitrogen were added successively with stirring, 0.5 ml. (5 millirnoles) of vanadyl trichloride and ml. of 1 molar (10 millirnoles) of aluminum triisobutyl in nhexane. After stirring the mixture for 10 minutes under the nitrogen blanket at 25 -27 C., the nitrogen source was cut off and an ethylene/propadiene gas stream in a mole ratio of 9/ 1 was passed into the catalyst suspension at a rate of approximately 160 ml. per minute. In an hour, polymer build-up was sufficient to make stirring inefiective. The gas flow was stopped and the catalyst was destroyed by mixing in 50 ml. of. methanol. The copolymer was isolated and purified by filtration and then by Washing in a Waring Blendor using, successively, 100

6 ml. of 5% concentrated hydrochloric acid in isopropanol, two 150 ml. portions of distilled water, and 100 ml. of methanol. The yield of polymer after rem-oval of solvent was 6.8 grams.

Infrared absorption of the polymer showed that the material contained units derived from both ethylene and propadiene; the proportion of ethylene units being approximately and the proportion of propadiene units 10%, is estimated upon the infrared absorption curves. Partial extraction with toluene in a Soxhlet extractor showed no composition change, indicating that a copolymer had been obtained. The copolymer had an inherent viscosity of 2.0 (0.1 gram copolymer in ml. of alpha-chloronaphthalene solution at l25 0.).

Two grams of the 9/1 mole ratio ethylene/propadiene copolymer was mixed with 5.0 gram-s of salicyclic acid, 0.5 gram of aluminum chloride, and 75 ml. of nitrobenzene. The mixture was shaken in a Parr shaker under nitrogen at 50 C. for 12 hours. The reactor contents were mixed with 10 ml. of 10% concentrated hydrochloric acid in isopropanol, Washed with copius quantities of hot water, dried and pressed into a film. Infrared scans showed the presence of 3.1 mole percent hydroxyl and aromatic groups in the polymer. The infrared absorption characteristic of the salicylyl radical was not eliminated or reduced by several extractions with hot toluene in a Waring Blendor or Soxhlet apparatus, which indicated that a true chemical transformation had occurred. The film displayed improved light stability.

Example 2 The procedure of Example 1 was repeated using 5.0 g. of boron triiiuoride etherate instead of aluminum chloride as catalyst. Infrared analysis showed the presence of 5.1 mole percent salicylyl groups in the copolymer.

The invention claimed is:

1. A modified copolymer of 65-99 mole percent of ethylene and 1-35 mole percent of propadiene, said modification being by reaction with a hydroxyl-containing aromatic acid selected from the group consisting of salicyclic acid, metahydroxybenzoic acid and para-hydroxybenzoic acid to provide 1-35 mole percent of a random selection of recurring units selected from the group consisting of where Z is hydroxybenzoyl.

2. The substantially linear polymer of claim 1 in the form of a shaped structure.

3. The substantially linear polymer of claim 1 in the form of a self-supporting film.

References Cited by the Examiner UNITED STATES PATENTS 3,043,818 7/19'62 'Icoker 260-882 FOREIGN PATENTS 776,326 6/ 1957 Great Britain.

WILLIAM H. SHORT, Primary Examiner.

I. C. MARTIN, Assistant Examiner. 

1. A MODIFIED COPOLYMER OF 65-99 MOLE PERCENT OF ETHYLENE AND 1-35 MOLE PERCENT OF PROPADIENE, SAID MODIFICATION BEING BY REACTION WITH A HYDROXYL-CONTAINING AROMATIC ACID SELECTED FROM THE GROUP CONSISTING OF SALICYCLIC ACID, METAHYDROXYBENZOIC ACID AND PARA-HYDROXYBENZOIC ACID TO PROVIDE 1-35 MOLE PERCENT OF A RANDOM SELECTION OF RECURRING UNITS SELECTED FROM THE GROUP CONSISTING OF 